Math Problem Statement

Evaluate the following limit or state that it does not exist: lim (x -> 0) [sin(5x) / sin(10x)]

Solution

The given limit is:

limx0sin(5x)sin(10x)\lim_{x \to 0} \frac{\sin(5x)}{\sin(10x)}

Solution:

  1. Direct Substitution: We cannot directly substitute x=0x = 0 because both sin(5x)\sin(5x) and sin(10x)\sin(10x) will be 0 at x=0x = 0, leading to the indeterminate form 00\frac{0}{0}.

  2. Apply Limit Properties: To resolve this, we can use the standard limit property: limx0sin(kx)kx=1\lim_{x \to 0} \frac{\sin(kx)}{kx} = 1 for any constant kk.

  3. Rewrite the Expression: We manipulate the limit expression by multiplying both the numerator and denominator by xx: limx0sin(5x)sin(10x)=limx0sin(5x)xsin(10x)x\lim_{x \to 0} \frac{\sin(5x)}{\sin(10x)} = \lim_{x \to 0} \frac{\frac{\sin(5x)}{x}}{\frac{\sin(10x)}{x}} Now, we can use the limit property: limx0sin(5x)5x×10xsin(10x)=510=12\lim_{x \to 0} \frac{\sin(5x)}{5x} \times \frac{10x}{\sin(10x)} = \frac{5}{10} = \frac{1}{2}

Thus, the value of the limit is: 12\boxed{\frac{1}{2}}

Would you like further clarification or details?


Here are 5 related questions:

  1. How would this limit change if the functions involved were sin2(5x)\sin^2(5x) and sin2(10x)\sin^2(10x)?
  2. What happens if we change the angle coefficients to different constants, say sin(3x)\sin(3x) and sin(7x)\sin(7x)?
  3. How do you calculate limits using L'Hopital's Rule in cases of indeterminate forms like 00\frac{0}{0}?
  4. What are some other common trigonometric limits that are frequently encountered?
  5. Can you explain the intuition behind the standard limit property limx0sin(kx)kx=1\lim_{x \to 0} \frac{\sin(kx)}{kx} = 1?

Tip:

When dealing with limits involving trigonometric functions, the small-angle approximation sin(x)x\sin(x) \approx x near zero is incredibly useful for resolving indeterminate forms.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric Limits

Formulas

lim (x -> 0) [sin(kx) / kx] = 1
lim (x -> 0) [sin(5x) / sin(10x)] = lim (x -> 0) [sin(5x)/x] / [sin(10x)/x]

Theorems

Standard Limit Property for Trigonometric Functions
Small-Angle Approximation

Suitable Grade Level

Grades 11-12 (High School Calculus), Undergraduate (Calculus I)